- ID:
- ivo://CDS.VizieR/J/ApJS/216/22
- Title:
- 3060-3700{AA} spectra analysis of early-type stars
- Short Name:
- J/ApJS/216/22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive and sensitive unbiased survey of interstellar features in the near-UV range (3050-3700{AA}). We combined a large number of VLT/UVES archival observations of a sample of highly reddened early-type stars -typical diffuse interstellar band targets- and unreddened standards. We stacked the individual observations to obtain a reddened "superspectrum" in the interstellar rest frame with a signal-to-noise ratio exceeding 1500. We compared this to the analogous geocentric and stellar rest frame superspectra as well as to an unreddened superspectrum to find interstellar absorption features. We find 30 known features (11 atomic and 19 molecular) and tentatively detect up to 7 new interstellar absorption lines of unknown origin. Our survey is sensitive to narrow and weak features; telluric residuals preclude us from detecting broader features. For each sightline, we measured fundamental parameters (radial velocities, line widths, and equivalent widths) of the detected interstellar features. We also revisit upper limits for the column densities of small, neutral polycyclic aromatic hydrocarbon molecules that have strong transitions in this wavelength range.
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- ID:
- ivo://CDS.VizieR/J/A+A/457/651
- Title:
- Abundance of nine beta Cephei stars
- Short Name:
- J/A+A/457/651
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Seismic modelling of the beta Cephei stars promises major advances in our understanding of the physics of early B-type stars on (or close to) the main sequence. However, a precise knowledge of their physical parameters and metallicity is a prerequisite for correct mode identification and inferences regarding their internal structure. Here we present the results of a detailed NLTE abundance study of nine prime targets for theoretical modelling: gamma Peg, delta Cet, nu Eri, beta CMa, xi1 CMa, V836 Cen, V2052 Oph, beta Cep and DD (12) Lac. The following chemical elements are considered: He, C, N, O, Mg, Al, Si, S and Fe. Our abundance analysis is based on a large number of time-resolved, high-resolution optical spectra covering in most cases the entire oscillation cycle of the stars.
- ID:
- ivo://CDS.VizieR/J/A+A/347/69
- Title:
- Abundances of halo early-type stars
- Short Name:
- J/A+A/347/69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present echelle (R~40,000) spectroscopic observations for a sample of apparently normal, high Galactic latitude, early-type stars drawn from the Palomar-Green Survey. The metal-line spectra show evidence for rotational velocity broadening with values of vsini<=300km/s. In conjunction with Kurucz model atmospheres, we derive stellar photospheric abundances that are consistent with a Population I chemical composition; differential abundances with respect to Galactic disk Population I stars indicate no abundance differences outside the estimated errors. From a comparison of the derived atmospheric parameters with recent theoretical evolutionary models, we derive distance and age estimates for individual stars. Using kinematical considerations, we conclude that all these objects are `runaway' stars, formed in the Galactic disk and subsequently ejected, possibly by supernovae explosions or dynamical interactions.
- ID:
- ivo://CDS.VizieR/J/A+A/547/A62
- Title:
- A catalogue of Paschen-line profiles
- Short Name:
- J/A+A/547/A62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have assembled an atlas of line profiles of the Paschen Delta (P-{delta}) line at 10049{AA} for the use of stellar modelling. For a few stars we have substituted the Paschen Gamma (P-{gamma}) line at 10938{AA} because the P-{delta} line blends with other features. Most of the targets are standard stars of spectral types from B to M. A few metal-poor stars have been included. For many of the stars we have also observed the Hydrogen Alpha (H-{alpha}) line so as to compare the profiles of lines originating from the meta-stable n=2 level with lines originating from the n=3 level. The greatest difference in line profile is found for high luminosity and cool stars where the departures from LTE in the population of the n=2 level is expected to be the greatest. For a few stars, sample line profiles have been calculated in the LTE approximation to demonstrate the usefulness of the tabulated and displayed catalogue.
- ID:
- ivo://CDS.VizieR/J/AN/329/801
- Title:
- Agglomerate of early-type Hipparcos stars
- Short Name:
- J/AN/329/801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the spatial structure and sub-structure of regions rich in Hipparcos stars with blue BT-VT colours. These regions, which comprise large stellar complexes, OB associations, and young open clusters, are tracers of on-going star formation in the Galaxy. The DBSCAN (Density-Based Spatial Clustering of Applications with Noise) data clustering algorithm is used to look for spatial overdensities of early-type stars. Once an overdensity, "agglomerate", is identified, we carry out a data and bibliographic compilation of their star member candidates. The actual membership in agglomerate of each early-type star is studied based on its heliocentric distance, proper motion, and previous spectro-photometric information. We identify 35 agglomerates of early-type Hipparcos stars. Most of them are associated to previously known clusters and OB associations. The previously unknown P Puppis agglomerate is subject of a dedicated study with Virtual Observatory tools.
- ID:
- ivo://CDS.VizieR/J/A+A/481/169
- Title:
- ATCA 3mm obs. of NGC 6334I and NGC 6334I(N)
- Short Name:
- J/A+A/481/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the dense gas, the outflows, and the continuum emission from the massive twin cores NGC 6334I and I(N) at high spatial resolution. We imaged the region with the Australia Telescope Compact Array (ATCA) at 3.4mm wavelength in continuum, as well as CH_3_CN (5_K_-4_K_) and HCN(1-0) spectral line emission.
- ID:
- ivo://CDS.VizieR/J/MNRAS/443/1555
- Title:
- ATLASGAL massive star forming clumps sample
- Short Name:
- J/MNRAS/443/1555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By matching infrared-selected, massive young stellar objects (MYSOs) and compact HII regions in the Red MSX Source survey to massive clumps found in the submillimetre ATLASGAL (APEX Telescope Large Area Survey of the Galaxy) survey, we have identified ~1000 embedded young massive stars between 280{deg}<l<350{deg} and 10{deg}<l<60{deg} with |b|<1.5{deg}. Combined with an existing sample of radio-selected methanol masers and compact HII regions, the result is a catalogue of ~1700 massive stars embedded within ~1300 clumps located across the inner Galaxy, containing three observationally distinct subsamples, methanol-maser, MYSO and HII-region associations, covering the most important tracers of massive star formation, thought to represent key stages of evolution.
- ID:
- ivo://CDS.VizieR/III/195
- Title:
- Atlas of Optical Spectral Classification OB Stars
- Short Name:
- III/195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Atlas provides digital spectra to assist the classification of OB spectra for 78 standard objects in the wavelength range 395.0-475.0 nm. Spectral types range from O3 - B3 (-B8 at Ia). The Atlas provides contemporary digital data comparable to the earlier printed Atlasses by Morgan et al. (1943), Abt et al. (1968), Yamashita et al. (1977) and Morgan et al. (1978). The digital data were obtained with the Shectman/Heathcote two- dimensional, photon-counting detector on the Casegrain spectrograph at the CTIO 1-meter telescope during October 1988 and March 1989. The 3-pixel resolution is 1.5 Angstroem, and the full wavelength coverage is 3800-5000 A. The data were extracted and rectified by using a uniform template followed by a low-order spine fit.
- ID:
- ivo://CDS.VizieR/J/A+A/506/213
- Title:
- B6-B9.5 stars abundance analysis
- Short Name:
- J/A+A/506/213
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CoRoT satellite is collecting precise time-resolved photometry for tens of asteroseismology targets. To ensure a correct interpretation of the CoRoT data, the atmospheric parameters, chemical compositions, and rotational velocities of the stars must be determined. The main goal of the ground-based seismology support program for the CoRoT mission was to obtain photometric and spectroscopic data for stars in the fields monitored by the satellite. These ground-based observations were collected in the GAUDI archive. High-resolution spectra of more than 200 B-type stars are available in this database, and about 45% of them is analysed here. To derive the effective temperature of the stars, we used photometric indices. Surface gravities were obtained by comparing observed and theoretical Balmer line profiles. To determine the chemical abundances and rotational velocities, we used a spectrum synthesis method, which consisted of comparing the observed spectrum with theoretical ones based on the assumption of LTE. Atmospheric parameters, chemical abundances, and rotational velocities were determined for 89 late-B stars. The dominant species in their spectra are iron-peak elements. The average Fe abundance is 7.24+/-0.45dex. The average rotational velocity is 126km/s, but there are 13 and 20 stars with low and moderate Vsini values, respectively. The analysis of this sample of 89 late B-type stars reveals many chemically peculiar (CP) stars. Some of them were previously known, but at least 9 new CP candidates, among which at least two HgMn stars, are identified in our study. These CP stars as a group exhibit Vsini values lower than the stars with normal surface chemical composition.
- ID:
- ivo://CDS.VizieR/J/A+A/613/A70
- Title:
- Be stars in the exofield of CoRoT. II.
- Short Name:
- J/A+A/613/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The class of Be stars are the epitome of rapid rotators in the main sequence. These stars are privileged candidates for studying the incidence of rotation on the stellar internal structure and on non-radial pulsations. Pulsations are considered possible mechanisms to trigger mass-ejection phenomena required to build up the circumstellar disks of Be stars. Time series analyses of the light curves of 15 faint Be stars observed with the CoRoT satellite were performed to obtain the distribution of non-radial pulsation (NRP) frequencies in their power spectra at epochs with and without light outbursts and to discriminate pulsations from rotation-related photometric variations. Standard Fourier techniques were employed to analyze the CoRoT light curves. Fundamental parameters corrected for rapid-rotation effects were used to study the power spectrum as a function of the stellar location in the instability domains of the Hertzsprung-Russell (H-R) diagram. Frequencies are concentrated in separate groups as predicted for g-modes in rapid B-type rotators, except for the two stars that are outside the H-R instability domain. In five objects the variations in the power spectrum are correlated with the time-dependent outbursts characteristics. Time-frequency analysis showed that during the outbursts the amplitudes of stable main frequencies within 0.03c/d intervals strongly change, while transients and/or frequencies of low amplitude appear separated or not separated from the stellar frequencies. The frequency patterns and activities depend on evolution phases: i) the average separations between groups of frequencies are larger in the zero-age main sequence (ZAMS) than in the terminal age main sequence (TAMS) and are the largest in the middle of the MS phase; ii) a poor frequency spectrum with f<1c/d of low amplitude characterizes the stars beyond the TAMS; and iii) outbursts are seen in stars hotter than B4 spectral type and in the second half of the MS. The two main frequency groups are separated by {delta}f=(1.24+/-0.28).f_{rot}_ in agreement with models of prograde sectoral g-modes (m=-1,-2) of intermediate-mass rapid rotators. The changes of amplitudes of individual frequencies and the presence of transients correlated with the outburst events deserve further studies of physical conditions in the subatmospheric layers to establish the relationship between pulsations and sporadic mass-ejection events.
